Re: [patch 14/21] Xen-paravirt: Add XEN config options anddisable unsupported config options.

From: Keir Fraser
Date: Fri Feb 16 2007 - 05:49:29 EST

On 16/2/07 08:37, "Dan Hecht" <dhecht@xxxxxxxxxx> wrote:

> Hmm? I thought the periodic timer and one-shot timer both generate the
> same VIRQ. So, how can you mask one without masking the other?
> The tickless idle works since the block hypercall disables the periodic
> timer. But for dynticks (aka NO_HZ), you'll need to mask the periodic
> timer (even for a running vcpu), while keeping the one-shot timer
> unmasked. I don't think Xen provides an interface to do that.

There's no interface for this right now, but we can easily add one in a
backward compatible way. This also will not prevent a dyntick kernel from
running on an older Xen -- the guest will then receive to many timer
interrupts, but that should only be a performance concern fixable by
upgrading the hypervisor component of the system.

-- Keir

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